Bones and skeletal system

1. 13
Date:
Roll no.:
PRACTICAL –4 Page no.:
Aim: To Study Identification of Axial bones
Axial Skeleton:
The axial skeleton is the part of the skeleton that consists of the bones of the head and
trunk of a vertebrate. In the human skeleton, it consists of 80 bones and is composed of
six parts; the skull bones, the ossicles of the middle ear, the hyoid bone, the rib cage,
sternum and the vertebral column.
The axial skeleton consists of 80 bones
 29 ones in the head - (8 cranial and 14 facial bones) and then also 7 associated
bones (6 auditory ossicles and the Hyoid Bone)
 25 bones of the thorax - (the sternum and 24 ribs)
 26 bones in the vertebral column (24 vertebrae, the sacrum and the coccyx)
The Skull:
 The bones of the skull support the structures of the face and protect the brain.
 The skull consists of 22 bones, which are divided into two categories: cranial
bones and facial bones.
Cranial bones
 They are eight bones that form the cranial cavity, which encloses the brain and
serves as an attachment site for the muscles of the head and neck.
 The eight cranial bones include the frontal bone, two parietal bones, two temporal
bones, the occipital bone, the sphenoid bone, and the ethmoid bone.
Facial bones
 They are 14, form the face, provide cavities for the sense organs (eyes, mouth, and
nose), protect the entrances to the digestive and respiratory tracts, and serve as
attachment points for facial muscles.
 The 14 facial bones are the nasal bones, maxillary bones, zygomatic bones,
palatine, vomer, lacrimal bones, inferior nasal conchae, and mandible.
Auditory ossicles
 Auditory ossicles of the middle ear transmit sounds from the air as vibrations to
the fluid-filled cochlea.
 The auditory ossicles consist of six bones: two malleus bones, two incus bones,
and two stapes, one of each on each side. These bones are unique to mammals.
Hyoid bone
 It lies below the mandible in the front of the neck. It acts as a movable base for the
tongue and is connected to muscles of the jaw, larynx, and tongue. The mandible
articulates with the base of the skull, controlling the opening to the airway and
gut. In animals with teeth, the mandible brings the surfaces of the teeth in contact
with the maxillary teeth.

2. 14
The Vertebral Column:
 The vertebral column, or spinal column, surrounds and protects the spinal cord,
supports the head, and acts as an attachment point for the ribs and muscles of
the back and neck.
 The adult vertebral column is comprised of 26 bones: the 24 vertebrae, the
sacrum, and the coccyx bones. In the adult, the sacrum is typically composed of
five vertebrae that fuse into one.
 The adult vertebrae are further divided into the 7 cervical vertebrae, 12 thoracic
vertebrae, and 5 lumbar vertebrae.
Each vertebral body has a large hole in the center through which the nerves of the spinal
cord pass. There is also a notch on each side through which the spinal nerves, which
serve the body at that level, can exit from the spinal cord. The names of the spinal
curves correspond to the region of the spine in which they occur. The thoracic and
sacral curves are concave, while the cervical and lumbar curves are convex. The arched
curvature of the vertebral column increases its strength and flexibility, allowing it to
absorb shocks like a spring.
Intervertebral discs composed of fibrous cartilage lie between adjacent vertebral bodies
from the second cervical vertebra to the sacrum. Each disc is part of a joint that allows
for some movement of the spine, acting as a cushion to absorb shocks from movements,
such as walking and running. Intervertebral discs also act as ligaments to bind vertebrae
together. The inner part of discs, the nucleus pulposus, hardens as people age,
becoming less elastic. This loss of elasticity diminishes its ability to absorb shocks.
The Thoracic Cage:
 The thoracic cage, also known as the ribcage, is the skeleton of the chest.
 It consists of the ribs, sternum, thoracic vertebrae, and costal cartilages.
 The thoracic cage encloses and protects the organs of the thoracic cavity,
including the heart and lungs.
 It also provides support for the shoulder girdles and upper limbs, and serves as
the attachment point for the diaphragm, muscles of the back, chest, neck, and
shoulders.
 Changes in the volume of the thorax enable breathing.
 The sternum, or breastbone, is a long, flat bone located at the anterior of the
chest. It is formed from three bones that fuse in the adult. The ribs are 12 pairs of
long, curved bones that attach to the thoracic vertebrae and curve toward the
front of the body, forming the ribcage. Costal cartilages connect the anterior ends
of the ribs to the sternum, with the exception of rib pairs 11 and 12, which are
free-floating ribs.
For further understanding reference: https://youtu.be/XmoTYdWz3tA
STUDY QUESTIONS
1. Functions of axial bones.
2. Draw a neat labeled diagram of Axial bones. Teacher’s sign:

3. 15
Date:
Roll no.:
PRACTICAL- 5 Page no.:
Aim: To Study Identification of Appendicular bones
Appendicular bones:
The human appendicular skeleton is composed of the bones of the upper limbs (which
function to grasp and manipulate objects) and the lower limbs (which permit
locomotion). It also includes the pectoral (or shoulder) girdle and the pelvic girdle, which
attach the upper and lower limbs to the body, respectively.
The Appendicular skeleton consist of 126 bones
 4 bones in the shoulder girdle (clavicle and scapula each side)
 6 bones in the arm and forearm (humerus, ulna and radius)
 58 bones in the hands (carpals 16, metacarpals 10, phalanges 28 and sesamoid 4
 2 pelvis bones
 8 bones in the legs (femur, tibia, patella and fibula)
 56 bones in the feet (tarsals, metatarsals, phalanges and sesamoid)
The Pectoral Girdle:
 The pectoral girdle bones, providing the points of attachment of the upper limbs to
the axial skeleton.
 It consists of the clavicle (or collarbone) in the anterior, as well as the scapula (or
shoulder blades) in the posterior.
 The clavicles, S-shaped bones that position the arms on the body, lie horizontally
across the front of the thorax (chest) just above the first rib.
 The scapulae are flat, triangular bones that are located at the back of the pectoral
girdle.
 They support the muscles crossing the shoulder joint.
 The spine runs across the back of the scapula; it is a good example of a bony
protrusion that facilitates a broad area of attachment for muscles to bone.
The Upper Limbs:
 The upper limbs contain 30 bones in three regions: the arm (shoulder to elbow),
the forearm (ulna and radius), and the wrist and hand.
 The humerus is the largest and longest bone of the upper limb and the only bone
of the arm. It articulates (joins) with the scapula at the shoulder and with the
forearm at the elbow.
 The forearm, extending from the elbow to the wrist, consists of two bones: the ulna
and the radius.
 The radius, located along the lateral (thumb) side of the forearm, articulates with
the humerus at the elbow.
 The ulna, located on the medial aspect (pinky-finger side) of the forearm, is longer
than the radius. It articulates with the humerus at the elbow.

4. 15
 The radius and ulna also articulate with the carpal bones and with each other,
which in vertebrates enables a variable degree of rotation of the carpus with
respect to the long axis of the limb.
 The hand includes the eight bones of the carpus (wrist), the five bones of the
metacarpus (palm), and the 14 bones of the phalanges (digits). Each digit consists
of three phalanges, except for the thumb, which, when present, has only two.
The Pelvic Girdle:
 The pelvic girdle attaches to the lower limbs of the axial skeleton and is
responsible for bearing the weight of the body and for locomotion.
 It is securely attached to the axial skeleton by strong ligaments. It also has deep
sockets with robust ligaments to securely attach the femur to the body.
 The pelvic girdle is further strengthened by two large hip bones.
 In adults, the hip bones are formed by the fusion of three pairs of bones: the ilium,
ischium, and pubis.
 The pelvis joins together in the anterior of the body the pubic symphysis joint and
with the bones of the sacrum at the posterior of the body.
The Lower Limbs:
 The lower limbs consist of the thigh, the leg, and the foot.
 The bones of the lower limb are the femur (thigh bone), patella (kneecap), tibia and
fibula (bones of the leg), tarsals (bones of the ankle), and metatarsals and
phalanges (bones of the foot).
 The bones of the lower limbs are thicker and stronger than the bones of the upper
limbs because of the need to support the entire weight of the body along with the
resulting forces from locomotion.
 The femur, or thighbone, is the longest, heaviest, and strongest bone in the body.
 The femur and pelvis form the hip joint at the proximal end.
 At the distal end, the femur, tibia, and patella form the knee joint.
 The patella, or kneecap, is a triangular bone that lies anterior to the knee joint; it
is embedded in the tendon of the femoral extensors (quadriceps). It improves knee
extension by reducing friction.
 The tibia, or shinbone, is a large bone of the leg that is located directly below the
knee. The tibia articulates with the femur at its proximal end, with the fibula and
the tarsal bones at its distal end.
 As the second largest bone in the human body it is responsible for transmitting
the weight of the body from the femur to the foot. The fibula, or calf bone, parallels
and articulates with the tibia. It is not weight-bearing, but acts as a site for muscle
attachment while forming the lateral part of the ankle joint.
 The tarsals are the seven bones of the ankle, which transmits the weight of the
body from the tibia and the fibula to the foot. The metatarsals are the five bones of
the foot, while the phalanges are the 14 bones of the toes.